Skill: Solve one-step subtraction word problems

First, find the whole amount and the amount that is taken away. Then subtract to find what remains.

Example:
A library has $(68{,}245)$ books. Students check out $(27{,}318)$ books. How many books are left?

1. Identify the quantities.

   • Whole: $(68{,}245)$ books
   • Part taken away: $(27{,}318)$ books
   • Unknown: books left

2. Write a subtraction equation.

$$68{,}245-27{,}318=\Box$$

3. Subtract by place value.

$$\begin{array}{r} 68{,}245\\ -27{,}318\\ \hline 40{,}927 \end{array}$$

You may need to regroup when the top digit is smaller than the bottom digit in a place.

4. State the answer with units.

   The library has $(40{,}927)$ books left.

5. Check using addition.

$$40{,}927+27{,}318=68{,}245$$

Since the sum matches the original whole, the answer is reasonable.